The invention relates to a storage apparatus and a load distribution method. The invention is suited for use in, for example, a storage apparatus having plural microprocessors.
Recently, load distribution techniques, i.e. techniques for distributing the load on microprocessors that process I/O requests sent from a host computer in a storage system, have been put into practical use.
For example, Japanese Patent Laid-Open Publication No. 2001-167040 proposes a storage subsystem in which I/O data transfer is controlled between a slave storage medium and a disk drive according to an I/O request received from an external master device, and that storage subsystem includes at least one external interface controller for each type of interface to each external master device that receives I/O requests, at least one control processor that processes the I/O requests, and a loop having Fibre Channel interfaces provided between the external interface controller and the control processor, the loop functioning as a transmission path for the external interface controller and the control processor.
In a storage subsystem with that configuration, the plural control processors process the I/O requests sent from a host computer in parallel, and the load is distributed among the control processors.
However, because of the overhead caused by the distribution loss generated during the load distribution processing in the above storage subsystem, the response time taken from the reception of an I/O request from a host computer until issue of a notice indicating the data processing relevant to the I/O request is complete, sometimes becomes longer than it would were the control processor that received the request completes the processing by itself.